Rename `root` parameter for all `Project` methods to `path`

[vyasr]

For consistency with the new terminology that we're standardizing on for both Job and Project, we should rename the root parameters of Project methods to path. This change affects get_project and init_project, as well as the Project constructor. Since we're moving forward with the breaking changes in #752, w should also change the signature of init_project to not require path to be a keyword-only argument. There may be other related changes as well that we need to consider, but I don't think there is any way to construct e.g. a Job at a specific path (we always construct by id or statepoint so I can't think of anything else that I might be missing right now.

Original comment
Do we want to keep the requirement that root is a keyword-only argument? All our previous discussions about compatibility layers are somewhat moot now, so I would be willing to revisit that.

It could even be named path for consistency with the new terminology. The more I think about it, it'd be really nice to call it path. :)

Originally posted by @bdice in #752 (comment)

[cbkerr]

Consider also replacing job.workspace() with something like job.path(). See #743

[vyasr]

@cbkerr already done in #685 and #752 😉

[bdice]

I'm looking into this issue.

[bdice]

I opened #758 to address this.

[kidrahahjo]

Can we close this issue now?

[bdice]

I think all the public APIs are fixed, based on the docs: https://docs.signac.io/projects/core/en/next/search.html?q=root&check_keywords=yes&area=default

There are a few lingering uses of the name "root" or "root directory" but they're in the context of import/export or migrations but they're typically used for walking a filesystem, not a project path, so I don't think this naming guidance applies.

There are also references to "root" in the context of synced collections, like the root of a collection, but those certainly don't need to be changed.

Marking as closed unless others wish to make further refactors.